Comprehensive analysis of environmental dispersion of buoyant particles in three-dimensional open-channel flows

Abstract

Understanding the environmental dispersion dynamics of buoyant particles in three-dimensional open-channel flows is vital for comprehending various ecological and hydraulic processes associated with open channels. This study employs Aris' concentration moment method to construct a model to assess the overall environmental dispersion characteristics of buoyant particle transport in the flow through a rectangular channel. Analytical solutions for concentration moments of buoyant particles are strictly derived using the separation of variables method. The overall characteristics of buoyant particle transport are analyzed using multiple-order concentration moments. Results show that the overall drift velocity Veff¯, the overall longitudinal dispersion Deff¯, and the overall skewness γ1¯ will eventually reach a stable state with different necessary times, jointly affected by R and Pez, where R is the aspect ratio and Pez reflects the relative strength of the vertical migration and the effective diffusion of buoyant particles. Veff¯ gradually increases with time for the three-dimensional laminar open-channel flow with R≈1 during the preliminary stage, in contrast to the gradual decrease in the corresponding two-dimensional flow. The skewness of the buoyant particles exhibits a mutual transformation between the positive and negative status. R primarily affects the concentration distribution of buoyant particles during the initial stage. Pez significantly influences the concentration distribution pattern throughout both the initial and long-term evolution of the buoyant particle cloud. The maximum cross-sectional average concentration of buoyant particles gradually decreases over time, with a substantial reduction rate in the open channel of small R.